Bad mesh, cannot continue

I am learning to use liggghts with tutorial examples.
The example of continuous blending mixer does not go through compiling and always gives an error of:

"WARNING: It is heavily recommended to use 'neigh_modify delay 0' with granular pair styles (../pair_gran.cpp:223)
Setting up run ...
Mesh cad1: 785 elements have high aspect ratio (soft limit: smallest angle > 0.500000 ° required)
WARNING: Fix mesh: Mesh contains highly skewed element, moving mesh (if used) will not parallelize well (../surface_mesh_I.h:575)
Mesh cad1: 221 mesh elements have a really unreasonably high aspect ratio (hard limit: smallest angle must be > 0.181185 °)
ERROR on proc 0: Fix mesh: Bad mesh, cannot continue. You will need to fix or remove these element. Remedies:
- You can use the 'element_exclusion_list' feature to remove elements with too many neighbors and elements with angles below the hard limit
(../surface_mesh_I.h:602)"
I added "heal auto_remove_duplicates" as suggested.
Please help. Any input is appreciated.
(The code is attached.)

Thanks.
Jing

Here is the displayed lines from running to error messages.
"
$ ./lmp_serial
LIGGGHTS (Version LIGGGHTS-PUBLIC 3.3.1, compiled 2016-01-15-10:28:32 by Administrator, git commit 99507f5217ad4fd4be5107d6262bd7274c9a5c03 based on LAMMPS 23 Nov 2013)
jump in.blend_mixer
Created orthogonal box = (-0.32 -1.96 -0.29) to (0.32 1.46 0.335)
1 by 1 by 1 MPI processor grid
Fix particledistribution/discrete (id pdd): distribution based on mass%:
pts: d=1.000000e-02 (max. bounding sphere) mass%=100.000000%
Fix particledistribution/discrete (id pdd): distribution based on number%:
pts: d=1.000000e-02 (max. bounding sphere) number%=100.000000%

Reading STL file 'meshes/trough2n.stl'

Reading STL file 'meshes/left_shaft2n.stl'

Reading STL file 'meshes/right_shaft2n.stl'
WARNING: It is heavily recommended to use 'neigh_modify delay 0' with granular pair styles (../pair_gran.cpp:223)
Setting up run ...
Mesh cad1: 785 elements have high aspect ratio (soft limit: smallest angle > 0.500000 ° required)
WARNING: Fix mesh: Mesh contains highly skewed element, moving mesh (if used) will not parallelize well (../surface_mesh_I.h:575)
Mesh cad1: 221 mesh elements have a really unreasonably high aspect ratio (hard limit: smallest angle must be > 0.181185 °)
ERROR on proc 0: Fix mesh: Bad mesh, cannot continue. You will need to fix or remove these element. Remedies:
- You can use the 'element_exclusion_list' feature to remove elements with too many neighbors and elements with angles below the hard limit
(../surface_mesh_I.h:602)
"